Showing papers on "Partial oxidation published in 2002"
TL;DR: In this paper, the resonance Raman detection of reduced molybdenum oxide phases is discussed in the above mentioned context of their active role in catalytic partial oxidation reactions. But this work was performed with a special sample of MoO2, which contained MoO 2, Mo4O11 and MoO3.
Abstract: A special sample was prepared by controlled oxidation of MoO2, which contained MoO2, Mo4O11 and MoO3, in order to extend the knowledge about the resonance Raman effect in reduced molybdenum oxides from those close to MoO3 to those close to MoO2. This knowledge is of paramount importance because technical partial oxidation catalysts often contain intermediate Mo oxides of the Magneli type, e.g. Mo4O11, or Mo5O14. The Raman spectra of orthorhombic Mo4O11 and MoO2 have been identified in a Raman microspectroscopic image of 100 single spectra recorded of a mixture of MoO3, MoO2 and Mo4O11. A resonance Raman effect was proven to be responsible for the detection of the molybdenum oxide phases Mo4O11 and MoO2 in dilution with BN when excited at a
laser wavelength of 632.8 nm by comparison with Raman microspectroscopic images of the identical sample when excited at 532 nm. The resonance Raman detection of reduced molybdenum oxide phases is discussed in the above mentioned context of their active role in catalytic partial oxidation reactions.
547 citations
TL;DR: In this article, the relationship between the catalytic performance of the binary MgO-based solid solution and its properties in the CO2 reforming, the partial oxidation and the steam reforming of methane is discussed.
Abstract: The excellent catalytic performance and high stability of MgO–NiO solid solution catalysts in CH4 conversion to syngas generated the recent outburst of interest for the binary MgO-based solid solutions. This review will focus on the relationship between the catalytic performance of the binary MgO-based solid solution and its properties in the CO2 reforming, the partial oxidation and the steam reforming of methane. First, the development of methane conversion to syngas will be summarized. Second, the role of the basicity and of the solid solution in the design of a catalyst that can inhibit carbon deposition and active metal sintering will be examined. Third, the main results regarding the catalytic performance of the MgO-based solid solutions will be presented. Fourth, detailed information regarding the effects of the NiO/MgO composition, surface area, pore distribution, crystal lattice parameter, precursors, and preparation condition on its catalytic behavior will be provided.
315 citations
TL;DR: In this paper, a simple power-law rate expression was fitted to experimental data in order to predict the rates of CO2 and H-2 formation under various reaction conditions, and the apparent activation energy (E-a) was estimated to be 100.9 kJ mol(-1) in good agreement with values reported in the literature.
308 citations
183 citations
TL;DR: In this article, a study was made of the iron species dislodged from the tetrahedral lattice position by thermal treatments in four Fe silicalite samples with Si/Fe ratios of 25, 50, 90, and 150.
164 citations
TL;DR: In this paper, the influence of catalyst properties on the activity and selectivity of hydrogen generation by methanol reforming over copper-based catalysts impregnated on γ-alumina pellets has been investigated.
Abstract: The influence of catalyst properties on the activity and selectivity of hydrogen generation by methanol reforming over copper-based catalysts impregnated on γ-alumina pellets has been investigated. In the experiments, three sets of copper-based catalysts with various compositions were tested: Cu/Zn/Al 2 O 3 , Cu/Cr/Al 2 O 3 and Cu/Zr/Al 2 O 3 . The catalysts were characterized using temperature programmed reduction (TPR), temperature programmed oxidation (TPO), SEM–EDS, Brunauer–Emmett–Teller (BET) surface area measurement and X-ray diffraction (XRD). The copper surface area was determined by pulse chemisorption using N 2 O. We found a correlation between the copper surface area and catalytic activity. The activity tests were performed in a fixed bed reactor with 15 g of spherical catalyst pellets using a gas hourly space velocity (GHSV) of 25,000. The results of the activity tests indicate that the choice of promoter and the catalyst composition greatly influence the activity as well as the selectivity for CO 2 formation. The highest conversions were achieved for the zinc-containing catalysts (Cu/Zn/Al 2 O 3 ) for both steam reforming and the combined reforming process. Complete conversion of methanol was only obtained for the zinc-containing catalysts when running the steam reforming process. The combined reforming process generally yielded a product stream containing lower carbon monoxide concentrations compared to steam reforming at the equivalent reactor temperature for all of the catalysts tested.
159 citations
TL;DR: In this article, the role of physicochemical properties of LaCoO3-CeO2-Co3O4 system with particular attention to the importance of phase segregation was investigated.
Abstract: The objective of this work is to understand the role of physicochemical properties of LaCoO3-CeO2-Co3O4 system with particular attention to the importance of phase segregation The catalytic materials used were all prepared by the citrate method They comprised: (i) single phase simple oxides and perovskites; (ii) in situ formed multiphase oxides of nominal compositions La1-xCexCoO3 (x = 0-05) prepared from a single solution precursor: (iii) lanthanum-cobalt mixed oxides impregnated with ceria by using cerium trinitrate; and (iv) mechanical mixtures of LaCoO3, CeO2 and Co3O4 Most of the materials were characterized by several methods (XRD, XPS, TPD-O-2) The activity of all of them was determined under the same conditions, using 01 g catalyst, 1% methane in air at a flowrate of 75 ml/min Partial replacement of lanthanum by cerium in LaCoO3 results in a significant improvement of activity, which can only partially be explained by the formation of a defective, perovskite related structure permitting higher oxygen mobility In La1-xCexCoO3 compositions with x > 005, segregation of ceria and other phases occurs The corresponding high activity seems to result from cooperation between the phases Some phase cooperation appears to occur even in the mechanically blended mixtures of LaCoO3-CeO2-Co3O4 While phase cooperation is well known in the case of partial oxidation catalysts, it had not been yet explicitly proposed as such in the case of total oxidation (combustion) catalysis (C) 2002 Elsevier Science BV All rights reserved
148 citations
TL;DR: In this article, the effect of the inclusion of Mo, Nb and Ta in Pt and PtRu carbon supported anode electrocatalysts on CO tolerance in proton exchange membrane fuel cells (PEMFC) was investigated by cyclic voltammetry and fuel cell tests.
144 citations
TL;DR: In this article, the authors showed that the addition of a small amount of Pd (0.145 mg cm 2 ) to anode significantly promoted the partial oxidation of methane by oxygen to form hydrogen and carbon monoxide, which resulted in electromotive forces of ca. 900 mV from the cell and extremely small electrode-reaction resistances of the anode.
Abstract: Electrocatalytic oxidation of methane over anodes in single-chamber solid oxide fuel cells, 0-10 wt % Pd-30 wt % Ce 0.8 Sm 0.2 O 1.9 (samaria-doped ceria, SDC)-Ni|SDC|Sm 0.5 Sr 0.5 CoO 3 , was studied in a mixture of methane and air between 450 and 550°C. The addition of a small amount of Pd (0.145 mg cm 2 ) to the anode significantly promoted the partial oxidation of methane by oxygen to form hydrogen and carbon monoxide, which resulted in electromotive forces of ca. 900 mV from the cell and extremely small electrode-reaction resistances of the anode. The peak power densities, when using a 0.15 mm thick SDC electrolyte, reached 644, 467, and 269 mW cm -2 at 550, 500, and 450°C, respectively.
141 citations
TL;DR: In this paper, a combined reformation system, which includes both auto-thermal catalytic and non-equilibrium plasma units, is studied experimentally for the practical application of hydrogen production via reforming of liquid gasoline-like fuels.
135 citations
TL;DR: In this article, a novel and ideal dense catalytic membrane reactor for the reaction of partial oxidation of methane to syngas (POM) was constructed from the stable mixed conducting perovskite material of BaCo0.4Fe 0.4Zr 0.2O3−δ and the catalyst of LiLaNiO/γ-Al 2O3.
Abstract: A novel and ideal dense catalytic membrane reactor for the reaction of partial oxidation of methane to syngas (POM) was constructed from the stable mixed conducting perovskite material of BaCo0.4Fe0.4Zr0.2O3−δ and the catalyst of LiLaNiO/γ-Al2O3. The POM reaction was performed successfully. Not only was a short induction period of 2 h obtained, but also a high catalytic performance of 96–98% CH4 conversion, 98–99% CO selectivity and an oxygen permeation flux of 5.4–5.8 ml cm−2 min−1 (1.9–2.0 μmol m−2 S−1 Pa−1) at 850 °C were achieved. Moreover, the reaction has been steadily carried out for more than 2200 h, and no interaction between the membrane material and the catalyst took place.
TL;DR: In this paper, a Ni-supported catalyst was prepared by the solid phase crystallization (spc) method starting from Mg-Al hydrotalcite (HT) anionic clay as the precursor; it was tested for the partial oxidation of CH4 to synthesis gas.
Abstract: Ni-supported catalyst was prepared by the solid phase crystallization (spc) method starting from Mg-Al hydrotalcite (HT) anionic clay as the precursor; it was tested for the partial oxidation of CH4 to synthesis gas. The precursor based on [Mg6Al2(OH)16CO32−]·4H2O was prepared by co-precipitation method from nitrates of the metal components. The precursor was then thermally decomposed and reduced to form Ni-supported catalyst (spc-Ni/Mg-Al). Ni2+ can well occupy the Mg2+ sites in the hydrotalcite resulting in the formation of highly dispersed Ni metal particles on spc-Ni/Mg-Al. The spc-Ni/Mg-Al thus prepared, showed high activity and selectivity to synthesis gas even at high space velocity. When Ni was supported by impregnating Mg-Al mixed oxide prepared from Mg-Al HT, the activity of imp-Ni/Mg-Al was higher than those of Ni/α-Al2O3 and Ni/MgO while it was close to that of spc-Ni/Mg-Al. The relatively high activity of the imp-Ni/Mg-Al may be due to the regeneration of Mg-Al HT phase from the mixed oxide during the preparation resulting in incorporation of Ni2+ on the Mg2+ sites in the HT as seen in the spc method.
TL;DR: In this paper, a ceria-supported platinum catalyst was used for catalytic partial-oxidation of CH 4 in air at atmospheric pressure on a solution-combustion method where platinum is present in ionically-substituted form.
Abstract: Fuel cell developers are investigating the generation of hydrogen from light hydrocarbons, such as methane or natural gas, for fuelling polymer electrolyte fuel cells (PEFCs) This study demonstrates generation of H 2 and CO by catalytic partial-oxidation of CH 4 in air at atmospheric pressure on a ceria-supported platinum catalyst prepared by a novel solution-combustion method where platinum is present in ionically-substituted form These catalysts at different platinum loadings showed methane conversion and hydrogen selectivity of 90 and 97%, respectively Interestingly, there is little carbon deposition in the catalytic reactor even after prolonged reaction time
TL;DR: In this article, the performance of fresh and used catalysts were characterized by nitrogen adsorption (BET method) for total surface area, and by H 2 and CO chemisorption or by the rate of propene hydrogenation for metal surface area.
Abstract: Partial oxidation of methane to synthesis gas over 0.5 wt.% Pt/Al_2O_3 and 0.5 wt.% Pt/CeO_2 catalysts was studied in a packed-bed reactor and supplementary runs of methane reforming with carbon dioxide were carried out. Fresh and used catalysts were characterized by nitrogen adsorption (BET method) for total surface area, and by H_2 and CO chemisorption or by the rate of propene hydrogenation for metal surface area. At temperatures up to 650°C, the Pt/CeO_2 catalyst gave considerably higher methane conversion and higher selectivity to CO and H_2 but above 700°C, the activities and selectivities of both catalysts were comparable. The Pt/CeO_2 catalyst maintained high selectivity to CO and H_2 when the CH_4:O_2 feed ratio varied from 1.7 to 2.3 while the Pt/Al_2O_3 catalyst had lower activity and selectivity under methane-rich conditions. The Pt/CeO_2 catalyst was also more active for methane reforming by carbon dioxide.
TL;DR: In this article, the partial oxidation of methane has been studied by sequential pulse experiments with CH4 → O2 → CH4 and simultaneous pulse reaction of CH4/O2 (2/1) over Ni/CeO2, Ni/ZrO2 and Ni/ceO 2 catalysts.
Abstract: The partial oxidation of methane has been studied by sequential pulse experiments with CH4 → O2 → CH4 and simultaneous pulse reaction of CH4/O2 (2/1) over Ni/CeO2, Ni/ZrO2 and Ni/Ce–ZrO2 catalysts. Over Ni/CeO2, CH4 dissociates on Ni and the resultant carbon species quickly migrate to the interface of Ni–CeO2, and then react with lattice oxygen of CeO2 to form CO. A synergistic effect between Ni and CeO2 support contributes to CH4 conversion. Over Ni/ZrO2, CH4 and O2 are activated on the surface of metallic Ni, and then adsorbed carbon reacts with adsorbed oxygen to produce CO, which is composed of the main path for the partial oxidation of methane. The addition of ceria to zirconia enhances CH4 dissociation and improves the carbon storage capacity. Moreover, it increases the storage capacity and mobility of oxygen in the catalyst, thus promoting carbon elimination.
TL;DR: In this paper, the mechanism of partial oxidation of methane was studied on Pt/Al2O3, Pt/ZrO2 and Pt/Ce-ZRO2 catalysts, and the reducibility and oxygen transfer capacity were evaluated by temperature programmed reduction and oxygen storage capacity.
TL;DR: In this article, three types of catalysts were tested: alumina, aluminosilicate material, and nickel-supported catalyst, and the results showed that the Ni-alumina or Ni-silica/aluminina formulations with Ca and/or K can significantly improve the steam capability.
Abstract: The gasification of biomass is a thermal treatment, which results in a high production of gaseous products and small quantities of char and ash. Steam reforming of hydrocarbons, partial oxidation of heavy oil residues, selected steam reforming of aromatic compounds, and gasification of coals and solid wastes to yield a mixture of H 2 and CO (syngas), followed by water-gas shift conversion to produce H 2 and CO 2 , are well-established processes. The steam capability can be significantly improved by permitting the classical Ni-alumina or Ni-silica/alumina formulations with Ca and/or K. Three types of catalysts were tested: alumina, aluminosilicate material, and nickel-supported catalyst.
TL;DR: In this paper, an oxygen permeating membrane for CH4 partial oxidation was investigated and it reached a value of 322 μmol/min cm2 (8 cm3/mincm2) at 1273 K and 0.5 mm thickness.
TL;DR: In this article, an aluminum-based micro-reactor was used to investigate the ammonia oxidation reaction on a supported polycrystalline platinum catalyst in the presence of a boundary layer.
TL;DR: In this article, Ni catalysts on perovskite-type CaTiO 3, SrTiO3, and BaTiO-3 oxides were prepared by the solid phase crystallization (SPC) method and tested for the partial oxidation of CH 4 to synthesis gas.
TL;DR: In this paper, a comprehensive characterisation of the catalyst SEM/EDX was performed at temperatures between 500 and 580 K and elevated pressures between 1.3 and 1.6 MPa.
TL;DR: In this paper, the results showed that the foam catalysts have high gas permeability, mechanical strength, thermostability and catalytic properties exceeding the ones of the traditional crystal and granular metal catalysts.
Abstract: Catalysts based on the foam metals (silver and copper) were studied in the processes of partial oxidation of methanol, ethanol and ethylene glycol. The experiments showed that the foam catalysts have high gas permeability, mechanical strength, thermostability and catalytic properties exceeding the ones of the traditional crystal and granular metal catalysts. Electronic states of silver and copper on the surface of the catalysts were studied by the method of diffuse reflectance electron spectroscopy in UV–VIS range.
TL;DR: In this paper, Ni, Rh and Ni containing catalysts obtained from hydrotalcite type precursors have been studied in the partial oxidation of methane and the results showed that the catalysts were characterised by HRTEM to evaluate the effectiveness of the preparation method in the dispersion of the metal.
TL;DR: In this paper, the authors analyzed the properties of combustion waves in an inert porous media for both methane and hydrogen sulfide combustion and found that up to 60% of the methane was converted to CO and H2.
TL;DR: In this paper, the authors proposed a combined cycle where natural gas is chemically treated to remove carbon, rather than being directly used as fuel, to avoid dispersion toward the atmosphere and the consequent contribution to the greenhouse effect.
Abstract: This paper discusses novel schemes of combined cycle, where natural gas is chemically treated to remove carbon, rather than being directly used as fuel. Carbon conversion to CO 2 is achieved before gas turbine combustion. Therefore CO 2 can be removed from fuel (rather than from exhausts, thus utilizing less demanding equipment) and made available for long-term storage, to avoid dispersion toward the atmosphere and the consequent contribution to the greenhouse effect. The strategy here proposed to achieve this goal is natural gas partial oxidation. The second part of the paper will address steam/methane reforming. Partial oxidation is an exothermic oxygen-poor combustion devoted to CO and H 2 production. The reaction products are introduced in a multiple stage shift reactor converting CO to CO 2 . Carbon dioxide is removed by means of physical or chemical absorption processes and made available for storage, after compression and liquefaction. The resulting fuel mainly consists of hydrogen and nitrogen, thus gas turbine exhausts are virtually devoid of CO 2 . The paper discusses the selection of some important parameters necessary to obtain a sufficient level of conversion in the various reactors (temperature and pressure levels, methane-to-air or methane-to-steam ratios) and their impact on the plant integration and on the thermodynamic efficiency. Overall performance (efficiency, power output, and carbon removal rate) is predicted by means of a computational tool developed by the authors. The results show that a net efficiency of 48.5 percent, with a 90 percent CO 2 removal, can be obtained by combined cycles based on large heavy duty machines of the present technological status, either by using chemical or physical absorption.
TL;DR: In this article, a commercial Cu/ZnO/Al2O3 catalyst was exposed to methanol reforming conditions in the presence of O2 and H2O, and a dependence of the copper oxidation state on the temperature was observed, with low temperatures favoring a higher oxidation state.
TL;DR: Vanadia adlayers of different coverage were prepared on TiO 2 (1/1/0) by codosing VOCl 3 and water as mentioned in this paper, and the mechanism of methanol oxidation was discussed.
TL;DR: In this article, the influence of the Fe loading on the catalytic pattern and steady-state properties of commercial silica catalysts has been evaluated, and the dispersion and coordination symmetry of surface Fe3+ species have been investigated by EPR analysis.
Abstract: The partial oxidation of methane to formaldehyde (MPO) with molecular O2 has been investigated on various bare and Fe-doped commercial silica catalysts at 650 °C. The influence of the Fe loading (0.01–3.2 wt.%) on the catalytic pattern and steady-state properties of the catalysts have been evaluated. The dispersion and coordination symmetry of surface Fe3+ species have been investigated by EPR analysis. “Isolated Fe3+ ions”, “small Fe2O3 clusters” and “Fe2O3 particles” are present on the surface of the FeOx/SiO2 catalysts, their relative concentration depending upon the loading. Iron species, irrespective of the state of aggregation, enable the reactivity of the silica surface, whilst the highest HCHO productivity is associated with an optimum surface Fe loading (0.05–0.1 Feat nm−2). The different reactivity of the various Fe-doped silica catalysts has been rationalised and normalised in terms of different concentration of “isolated Fe3+ species” and “aggregated Fe2O3 moieities”.
TL;DR: The selective oxidation of n-butane to maleic acid catalyzed by vanadium phosphates (VPO) is one of the most complex partial oxidation reactions used in industry today and an experimental protocol to study the mechanism is developed in which (13)C-isotopically labeled n- butane is flowed over a catalyst bed and the reaction products are analyzed using NMR spectroscopy.
Abstract: The selective oxidation of n-butane to maleic acid catalyzed by vanadium phosphates (VPO) is one of the most complex partial oxidation reactions used in industry today. Numerous reaction mechanisms have been proposed in the literature, many of which have butenes, butadiene, and furan as reaction intermediates. We have developed an experimental protocol to study the mechanism of this reaction in which (13)C-isotopically labeled n-butane is flowed over a catalyst bed and the reaction products are analyzed using (13)C NMR spectroscopy. This protocol approximates the conditions found in an industrial reactor without requiring an exorbitant amount of isotopically labeled material. When [1,4-(13)C]n-butane reacted on VPO catalysts to produce maleic acid and butadiene, the isotopic labels were observed in both the 1,4 and 2,3 positions of butadiene and maleic acid. The ratio of label scrambling was typically 1:20 for the 2,3:1,4 positions in maleic acid. For butadiene, the ratio of label scrambling was consistently much higher, at 2:3 for the 2,3:1,4 positions. Because of the discrepancy in the amount of label scrambling between maleic acid and butadiene, butadiene is unlikely to be the primary reaction intermediate for the conversion of n-butane to maleic anhydride under typical industrial conditions. Ethylene was always observed as a side product for n-butane oxidation on VPO catalysts. Fully (13)C-labeled butane produced about 5-13 times as much isotopically labeled ethylene as did [1,4-(13)C]butane, indicating that ethylene was produced mainly from the two methylene carbons of n-butane. When the reaction was run under conditions which minimize total oxidation products such as CO and CO(2), the amounts of ethylene and carbon oxides produced from fully (13)C-labeled butane were almost equal. This strongly suggests that the total oxidation of n-butane on VPO catalysts involves the oxidation and abstraction of the two methyl groups of n-butane, and the two methylene groups of n-butane form ethylene. An organometallic mechanism is proposed to explain these results.
TL;DR: In this article, a series of molybdenum carbide catalysts were prepared using 10% C 2 H 2 /H 2 to carburize moly bdenum trioxide at different temperatures, and their performance was evaluated using methane partial oxidation to synthesis gas as the model reaction.